In vehicles, position determination devices such as satellite navigation receivers are often used for determining a position. The position data of the vehicle determined in this manner can then be used, for example, for navigation devices for vehicle navigation. The navigation devices are permanently installed in the vehicle or can be arranged as mobile units in the vehicle.
In today's systems, the GPS signal is often accepted as given. To improve the accuracy of a position signal which is determined from GPS data, differential GPS (DGPS) can be used, for example.
If the vehicle position thus obtained is used by a driver assistance system or a safety system, these systems must often assume, for safety reasons, that the position is inaccurate. This is the case particularly when the satellite reception is disturbed. An inaccurate position determination is also disadvantageous if an automated emergency call containing the vehicle position is to be initiated.